Lubricating Base Oils from Esterified Alkoxylated Polyols Using Saturated Long-Chain Fatty Acids

ABSTRACT

The present disclosure relates to methods and compositions for making bio-based, biodegradable, and non-bioaccumulating lubricating base oils generated by esterifying alkoxylated polyols (average alkoxylation ≥3) with long-chain (≥C14) saturated and unsaturated fatty acids (FA) or fatty acids modified using industry recognized techniques.

This disclosure was developed with the use of funds from the NationalScience Foundation Grant 1555998, Department of Energy GrantDE-SC0018751 and USDA Grant 2018-33610-28260. The Government has certainrights in the invention.

FIELD OF THE INVENTION

The present disclosure relates to methods and compositions for makingbio-based, biodegradable, and non-bioaccumulating lubricating base oilsgenerated by esterifying alkoxylated polyols (average alkoxylation ≥3)with long-chain (≥C14) saturated and unsaturated fatty acids (FA) orfatty acids modified using industry recognized techniques.

BACKGROUND OF THE INVENTION

Lubricant demand and usage are expected to steadily increase over thecoming years. Along with the increased demand, performance requirementsare also changing, leading to the development of novel andhigh-performance lubricants. Lubricants are expected to carry greaterloads at longer drain intervals while simultaneously providing increasedmechanical efficiency and lower risk of environmental contamination.Because of the increased expectations, original equipment manufacturers(OEM) and end users are in need of lubricants that are significantlymore robust than the Group I and Group II petroleum lubricants that arewidely available at low cost.

Current replacement options are severely hydrotreated mineral oils(Group III/III+), polyalphaolefin (PAO, Group IV), and other syntheticlubricants (Group V). The Group V oils encompass a wide range ofmaterials including vegetable oils, synthetic esters, polyalkyleneglycols, and naphthenic oils. All of the replacement options haveassociated cost increases and/or material specific performancelimitations relative to the more common Group I/II base oils.

Viscosity is the one of the most important physical property for alubricating oil. Different applications require varied viscosities basedon the operating conditions of a given system.

For petroleum derived lubricants (Group III/III+ and PAO) high viscositylubricants (>ISO VG 150) are costly to produce and have relatively poorviscosity indices, while ultra-low viscosity lubricants (<ISO VG 22)have significant amounts of volatile components creating issues withfire and flash stability and evaporative loss. The best applications forthese lubricants are those that require ISO VG 32-100, are not run atexcessive temperatures, and are not areas of environmental concern.

Synthetic esters can be made to span a broad range of viscosities butare generally costlier on a per kg basis. Additionally, to meet higherviscosities (ISO VG>100) pour point is severely affected, limitingoperational conditions for the lubricants. Synthetic esters tend to havehigh flash and fire points and are generally more environmentallyfriendly than petroleum derived lubricants. The best applications forthese lubricants are those that require ISO VG 22-46, are not prone toprolonged high load use, and require high temperature safety due to firerisk.

Vegetable oils are environmentally friendly, fire and flash stable, andprovide excellent wear resistance and lubricity. The most significantdrawback to them is thermal and oxidative stability. Vegetable oils tendto oxidize rapidly at elevated temperatures and tend to crystallize orsolidify at near zero temperatures. The best applications of theselubricants are those that require ISO VG 32-68, where temperatures arestrictly controlled, and where contamination or leaks are of health andenvironmental concern.

Various lubricants have been disclosed. For example, U.S. Pat. No.3,337,595 discloses the making of fatty acid esters of propoxylatedglycerol for use as defoaming aids. The preferred embodiment of the artis diesters of propoxylated glycerol and blends of said diesters withfatty acid methyl esters and esters of polyethylene glycol.

U.S. Pat. No. 3,530,070 discloses the use of propoxylated polyols assynthetic lubricants. The compositional space encompasses multiplepolyols (trimethylol propane, neopentyl glycol, pentaerythritol,dipentaerythritol, sorbitol, and glycerol) propoxylated up to an averageof 72 PO units per mole of polyol and esterified to various fatty acids(≤C12).

U.S. Pat. No. 4,031,118 is concerned with ester containing processes andcompositions. The compositions disclosed are high MW (1000-10000 g/mol)polyether polyols esterified with very long chain (≥C30) fatty acids.

U.S. Pat. No. 5,916,854 discloses the use and composition ofinteresterified and alkoxylated lubricating oils. The compositions areproduct by process entailing the interesterification of natural oilswith glycerol or free fatty acids with simultaneous alkoxylation. Theresultant products are a blend of many different compositions includingmonoesters, diesters, and linear esters.

PCT WO1995002659 discloses lubricating oil compositions for use ashydraulic fluids. Two processes are used to generate the claimedcompositions:

-   -   a.) Propoxylation of glycerol to an average of <3 PO units per        glycerol with preferred embodiments of 1 PO unit per glycerol        followed by esterification with FA from C6-C24    -   b.) One pot process like that listed under U.S. Pat. No.        5,916,854 creating product by process.

PCT WO2012134792 discloses a lubricant composition comprising polymersof glycerol that have been propoxylated to an average of 6-15 PO unitsfollowed by esterification with FA from C8-C15. Preferred claims arealkoxylates (PO 8-12) and FA esters (C9-11) of digylcerol andtriglycerol.

PCT WO2014124698 concerns the composition and use of ester lubricants.The compositions claimed and described concern propoxylatedpentaerythritol esterified with various fatty acids.

What is needed in the art is the use of long-chain fatty acid insignificant quantities in combination with alkoxylated polyols whilemaintaining pour point temperatures and viscosities characteristic of alubricating oil. Prior disclosures have utilized room temperature fluidor very low melting FA to control thermal and viscometric properties ofthe base oil. This disclosure substantially utilizes high melting FA,controlling thermal and viscometric properties by manipulating thedegree of alkoxylation and minor fatty acid components of theesterification product.

SUMMARY OF THE INVENTION

The above objectives are accomplished according to the presentdisclosure by providing in a first embodiment, a synthetic esterlubricating base oil. The base oil may comprise at least one alkoxylatedpolyol, wherein the average degree of alkoxylation is from ≥3 and atleast one fatty acid, wherein the fatty acid is substantiallylong-chain, equal to or greater than C14. Further the at least onealkoxylated polyol may comprise glycerol, trimethylol propane, neopentylglycol, or sorbitol. Further yet, the at least one alkoxylated polyolmay comprise propoxylated glycerol. Still yet, the at least one fattyacid may be substantially fully saturated. Further still, the at leastone fatty acid may be substantially unsaturated. Yet still, the at leastone fatty acid may comprise fatty acids with chain lengths <C14. Furtheragain, the source for the at least one fatty acid may be substantiallywhole cut. Still again, the at least one fatty acid may be adicarboxylic acid. Yet again, the at least one substantially fullysaturated fatty acid may comprise 12-hydroxystearic acid. Again still,the at least one fatty acid may be functionalized and thefunctionalization may comprise epoxidation, maleination, metathesis,amidation, halogenation, hydration, estolide formation, orvulcanization. Again still, the lubricating base oil may have a pourpoint of at or below −10° C. Still yet further, the lubricating base oilmay be at least 60 percent biodegradable. Yet again further, thelubricating base oil may be at least 50 percent bio-based. Further yetstill, the lubricating base oil may form a base for a grease. Yet againstill, the lubricating base oil may comprises a process oil or rubberextender oil. Yet still, the lubricating base oil may comprise adielectric fluid.

In a further embodiment, a method is provided for forming a syntheticester lubricating base oil. The method includes alkoxylating at leastone polyol backbone, wherein the average degree of alkoxylation is from≥3 and esterifying the at least one alkoxylated polyol backbone with atleast one fatty acid, wherein the at least one fatty acid issubstantially long-chain, equal to or greater than C12. Further, the atleast one fatty acid may be saturated. Yet further, the at least onefatty acid may be unsaturated. Still yet, the at least one fatty acidmay be substantially long-chain, equal to or greater than C14. Yetagain, the method may include functionalizing the at least one fattyacid. Still yet further, functionalization may include epoxidation,maleination, metathesis, amidation, halogenation, hydration, estolideformation, hydroxy functionalization, or vulcanization. Again further,the method includes forming the lubricating base oil into a base for agrease.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction designed to carry out the invention will hereinafter bedescribed, together with other features thereof. The disclosure will bemore readily understood from a reading of the following specificationand by reference to the accompanying drawings forming a part thereof,wherein an example of the disclosure is shown and wherein:

FIG. 1 shows Scheme A: Reaction scheme for the synthesis of esterifiedpropoxylated glycerol from the propoxylated glycerol and fatty acidsbase components.

FIG. 2 shows a wireframe rendering of the 3D design space utilized inthe demonstration of Examples 1-72.

FIG. 3 shows Table A: Base oil property data for examples 1-24.

FIG. 4 shows Table B: Base oil property data for examples 25-48.

FIG. 5 shows Table C: Base oil property data for examples 49-72.

FIG. 6 shows pour point data for examples 1-72 as a function ofmolecular weight.

FIG. 7 shows kinematic viscosity (40° C.) data for examples 1-72 as afunction of molecular weight.

FIG. 8 shows kinematic viscosity (100° C.) data for examples 1-72 as afunction of molecular weight.

FIG. 9 shows Table D: Lubricant specific data comparison for examples73-79 and John Deere HyGard Transmission and Hydraulic OIL.

FIG. 10 shows Table E: Base oil properties for modified base oilexamples 80-84.

FIG. 11 shows molecular diagrams for adipic, sebacic, and12-hydroxystearic acids.

FIG. 12 shows Table F: Dielectric fluid test data comparison for example85 and two commercial biodegradable dielectric fluids.

FIG. 13 shows Table G: Base oil data for esterified ethoxylated glycerolsamples with coconut, stearic, lauric acids.

It will be understood by those skilled in the art that one or moreaspects of this disclosure can meet certain objectives, while one ormore other aspects can meet certain other objectives. Each objective maynot apply equally, in all its respects, to every aspect of thisdisclosure. As such, the preceding objects can be viewed in thealternative with respect to any one aspect of this disclosure. These andother objects and feature of the disclosure will become more fullyapparent when the following detailed description is read in conjunctionwith the accompanying figures and examples. However, it is to beunderstood that both the foregoing summary of the disclosure and thefollowing detailed description are of a preferred embodiment and are notrestrictive of the disclosure or other alternate embodiments of thedisclosure. In particular, while the disclosure is described herein withreference to a number of specific embodiments, it will be appreciatedthat the description is illustrative of the disclosure and is notconstructed as limiting of the disclosure. Various modifications andapplications may occur to those who are skilled in the art, withoutdeparting from the spirit and the scope of the disclosure, as describedby the appended claims. Likewise, other objects, features, benefits andadvantages of the present disclosure will be apparent from this summaryand certain embodiment described below, and will be readily apparent tothose skilled in the art. Such objects, features, benefits andadvantages will be apparent from the above in conjunction with theaccompanying examples, data, figures and all reasonable inferences to bedrawn therefrom, alone or with consideration of the referencesincorporated herein.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to the drawings, the disclosure will now be described inmore detail. Unless defined otherwise, all technical and scientificterms used herein have the same meaning as commonly understood to one ofordinary skill in the art to which the presently disclosed subjectmatter belongs. Although any methods, devices, and materials similar orequivalent to those described herein can be used in the practice ortesting of the presently disclosed subject matter, representativemethods, devices, and materials are herein described.

Unless specifically stated, terms and phrases used in this document, andvariations thereof, should be construed as open ended as opposed tolimiting. Likewise, a group of items linked with the conjunction “and”should not be read as requiring that each and every one of those itemsbe present in the grouping, but rather should be read as “and/or” unlessexpressly stated otherwise. Similarly, a group of items linked with theconjunction “or” should not be read as requiring mutual exclusivityamong that group, but rather should also be read as “and/or” unlessexpressly stated otherwise.

Furthermore, although items, elements or components of the disclosuremay be described or claimed in the singular, the plural is contemplatedto be within the scope thereof unless limitation to the singular isexplicitly stated. The presence of broadening words and phrases such as“one or more,” “at least,” “but not limited to” or other like phrases insome instances shall not be read to mean that the narrower case isintended or required in instances where such broadening phrases may beabsent.

The lubricating base oils of the present disclosure combine thelubricity and wear resistance of vegetable oils, the low temperaturepour points of synthetic esters, and the range of viscosities of the“synthetic” petroleum derivatives, while being lower cost than bothcurrent synthetic esters and Group III+/PAO lubricants.

By utilizing long chain fatty acid(s) in conjunction with alkoxylatedpolyol(s), this disclosure generates base oils that have high bio-basedcontent (>60 wt. %, such as >65, >70, >75, >80, >85, >90, >95, etc.),and high biodegradability. Bio-based content refers to materials whichare derived from biological products or renewable domestic agriculturalmaterials (including plant, animal, and marine materials) or forestrymaterials or an intermediate feedstock. Biodegradability refers to theability of a material to be decomposed by bacteria or other livingorganisms.

The above objectives are accomplished according to the presentdisclosure by providing in a first embodiment, a lubricating base oil.The lubricating base oil may include an alkoxylated polyol combined withat least one saturated fatty acid source to form an esterifiedalkoxylated polyol. Further, the esterified alkoxylated polyol comprisesesterified propoxylated glycerol (EPG). Still further, the lubricatingbase oil is at least 40 percent biodegradable, such as for purposes ofexample only and not intended to be limiting 45 percent, 50, 55, 60, 65,70, 75, 80, 85, 90, 95, etc., more preferably the lubricating base oilis at least 50 percent biodegradable, and most preferably thelubricating base oil is at least 60 percent biodegradable. Yet further,the base oil has an average degree of alkoxylation of greater than orequal to 3, such as 4, 5, 6, 7, 8, 9, 10 or greater. Further still, atleast one fatty acid source comprising the oil is substantiallylong-chain (>C14, such as C15, C16, C17, C18, C19, C20, C21, C22, C23,C24, C25, C26, C27, C28, C29, C30, or longer) fatty acids. Even further,at least one fatty acid source comprising the oil is substantiallyunsaturated fatty acid. Even still further, the oil has a pour point ator below 0° C., and more preferably below −10° C., such as −15, −20,−25, −30, −35, −40, etc. Further yet, at least one fatty acid source maysubstantially be whole cut. Whole cut fatty acids are products of thedirect fat splitting of natural oils and substantially comprise thenative fatty acid composition of a representative natural oil. For thepurposes of this disclosure, the whole cut fatty acid may be “cleaned”as understood by those of skill in the art and/or partiallyfractionated. Further, specific cuts, such as for purpose of exampleonly but not intended to be limiting, high melt point cuts, may also beemployed. Suitable whole cut fatty acids may be derived from vegetableor seed oils such as coconut oil, palm oil, palm kernel oil, palm fattyacid distillate soybean oil, rapeseed oil, canola oil, high oleicsoybean oil, sunflower oil, corn oil, cottonseed oil, castor oil, oliveoil, safflower oil, or linseed oil. Whole cut fatty acids may also bederived from animal oils such as fish oil, lard, tallow, or whale oil.Even further, the oil may include multifunctional fatty acids which mayconsist of dicarboxylic acids, hydroxy functional acids, or acidsmodified by techniques that may include but are not limited toepoxidation, maleination, metathesis, amidation, halogenation,hydration, or estolide formation.

In a further embodiment, a method is provided for forming a lubricatingbase oil. The method includes alkoxylating a polyol backbone andesterifying the alkoxylated polyol backbone with a saturated fatty acid,unsaturated fatty acid, or both to produce an esterified alkoxylatedpolyol. Further, the alkoxylated polyol comprises esterifiedpropoxylated glycerol. Still further, the lubricating base oil is atleast 60 percent biodegradable and may be 65, 70, 75, 80, 85, 90, or 95percent or higher. Further yet, the base oil has an average degree ofalkoxylation of equal to or greater than 3, such as 5, 7, etc. Still yetfurther, that at least one saturated fatty acid is equal to or greaterthan C12 saturated fatty acids, such as C13, C14, C15, C16, C17, C18, orhigher. Even further, the saturated fatty acid is equal to or greaterthan C14, such as C15, C16, C17, C18, C19, C20, C22, C23, C24, C25, orhigher. Yet still, the oil has a pour point of at or below −10° C., suchas −15, −20, −25, −30, −35, −40, etc. Further yet, changing the feedratio of at least one saturated fatty acid allows for tailoringproperties of the lubricating base oil. Still further, that at least onesaturated fatty acid source is whole cut. Still even further, at leastone dicarboxylic acid is added as the esterified propoxylated polyol isformed. Yet still, that at least one saturated fatty acid comprises12-hydroxystearic acid.

Some embodiments described herein are related to the synthesis and useof fatty acid esters of polyol alkoxylates, which possess viscositiescharacteristic of lubricating oils, have viscosity indices greater than140, such as 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200,or higher, have pour points ≤0° C., such as −5, −10, −15, −20, −25, −30,−35, −40, etc. and are bio-based, biodegradable, and non-bioaccumulatingalternatives to petroleum derived lubricating oils. A more preferredembodiment would consist of fatty acid esters of polyol alkoxylates withviscosity indices greater than 160, pour points ≤−10° C., bio-basedcontent greater than 50%, and biodegradability greater than 40%, such as45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or higher. Even further amore preferred embodiment would consist of fatty acid esters of polyolalkoxylates with viscosity indices greater than 180, pour points ≤−10°C., bio-based content greater than 55%, and biodegradability greaterthan 60%.

The polyol component of the present disclosure may be one or multiplecommon polyol substances such as, neopentyl glycol, trimethylol propane,glycerol, pentaerythritol, sorbitol, dipentaerythritol, orpolyglycerols. The preferred polyol of this embodiment is glycerol.

The alkylene oxide component used to generate the polyol alkoxylate(polyether polyol) may consist of one or multiple alkylene oxides suchas: ethylene oxide, propylene oxide, or butylene oxide. The alkoxylatedpolyol may contain ≥3 substituent alkoxy groups per polyol molecule. Thepreferred alkylene oxide of this embodiment is propylene oxide. Thepreferred degree of alkoxylation is ≥3 alkoxy groups per glycerolmolecule, more preferably ≥5 alkoxy groups per glycerol molecule, andmost preferably ≥10 alkoxy groups per glycerol molecule.

The fatty acid component of the esterified alkoxylated polyol mayconsist of saturated, unsaturated, or a combination of both saturatedand unsaturated monobasic fatty acids with chain lengths of 4-24carbons. The fatty acid component may also consist of saturated,unsaturated, or a combination therein of dibasic fatty acids with chainlengths ≥6 carbons. The fatty acid component may also consist ofsaturated, unsaturated, or a combination therein of hydroxy fatty acids.The fatty acid component may also consist of saturated, unsaturated, ora combination therein of branched fatty acids. The preferred fatty acidsof this embodiment are both saturated and unsaturated monobasic fattyacids with chain lengths of 8-18 carbons.

The alkoxylated polyol may be synthesized utilizing common techniquesknown to those skilled in the art or may be acquired given a suitablecommercially available source. The fatty acids may be derived fromnatural oils utilizing common techniques known to those skilled in theart or may be acquired from a suitable commercially available source.The esterification of the fatty acids and the alkoxylated polyol may beconducted with or without a catalyst utilizing techniques known to thoseskilled in the art. Non-catalyzed esterification may require theaddition of molar excesses of fatty acid to the reaction mixture,reaction temperatures exceeding 150° C., application of vacuum to removewater, or a combination of said reaction parameters. Catalyzedesterification may be conducted at stoichiometric ratios of fatty acidto alcoholic hydroxyl, at temperatures below or above 150° C., atambient pressure, or a combination of said reaction parameters. Suitablecatalysts for the esterification of the alkoxylated polyol may includebut are not limited to Iron (II) chloride, Titanium (IV)oxyacetylacetonate, Silica chloride, Graphene oxide, Sulfuric acid,Methanesulfonic acid, p-Tolunesulfonic acid, or Scandium (III) Triflate.

For the purposes of this embodiment the alkoxylated polyol was acquiredfrom commercial sources and consisted of propoxylated glycerol with anaverage of 10 alkoxy groups per glycerol. The product is commonlysupplied as 700 molecular weight glycerol-initiated polyether polyol(BASF: Pluracol GP730, Dow: Voranol 2070, Monument: Poly-G 30-240,Carpenter, Carpol GP700). For the purposes of this embodiment pure fattyacids utilized were selected from lauric (C12), myristic (C14), palmitic(C16), stearic (C18 sat.), and oleic (C18 unsat.). For the purposes ofthis embodiment whole cut fatty acids were also utilized and consist ofcoconut fatty acids, hydrogenated coconut fatty acids, soy fatty acids,canola fatty acids, and high oleic soy fatty acids.

The esterified propoxylated glycerol lubricant base oils of the presentdisclosure were prepared by charging an appropriate reaction vessel withthe propoxylated glycerol and a 10% molar excess of the required fattyacid(s). The esterification was carried out at 240-250° C. and run undervacuum until the acid value of the reaction mixture was below about 15mg KOH/g and the hydroxyl value of the reaction mixture was below about20 mg KOH/g. Excess fatty acid and volatile reaction by products werethen removed via short path distillation under vacuum and elevatedtemperature. Common ester purification techniques may be utilized in theabsence of short path distillation. The ester product of the reactionwas purified to an acid value <1 mg KOH/g with a preferred acid value<0.5 mg KOH/g, and a hydroxyl value <10 mg KOH/g with a preferredhydroxyl value <5 mg KOH/g.

The structure of the esterified propoxylated glycerol lubricating oilcan be seen in Scheme A, see FIG. 1, which shows esterification ofpropoxylated glycerol (x+y+z=average degree of propoxylation) with fattyacid. One aspect of the present disclosure is that the polyethersegments separating the glycerol (polyol) backbone and fatty acid chainscharacteristic of natural oils (synthetic esters) provide increasedflexibility in the molecule enabling significant reductions in pourpoint compared to a natural oil or synthetic esters with an identicalfatty acid profile. This lability in the molecule facilitates the use ofhigher fatty acids while maintaining the low pour points observed foresterified propoxylated glycerol lubricating oils. Another aspect of thepresent disclosure is that introduction of the polyether segmentsprovides increased thermal and oxidative stability for the esterifiedpropoxylated glycerol lubricants when compared to natural oils andnon-neopentyl synthetic esters. A further aspect of the presentdisclosure is the use of long chain fatty acids to increase loadcarrying capacity of the lubricating base oil when compared to mid-chainfatty acid (C8-C11) synthetic esters. An additional aspect of thedisclosure is an increase in detergency owing to the polyether segmentsof the base oil molecule as compared to common synthetic esters.

One aspect of the present disclosure is the functionalization of thefatty acid functionality of the esterified propoxylated glycerollubricating base oil. Common techniques, known to those skilled in theart, may be used to modify the fatty acid chains to impart desiredperformance characteristics which may include epoxidation, maleination,metathesis, amidation, halogenation, hydration, estolide formation, orvulcanization.

One aspect of the present disclosure is the use of the esterifiedpropoxylated glycerol as a lubricating base oil, either neat or as aformulated product, in Industrial Lubricants: gear oils, R&O compressoroils, R&O turbine oils; Automotive Oils: crankcase oils, transmissionoils, gear oils; Metalworking Fluids; Marine Lubricants; Grease; ProcessOils, or Dielectric Fluids.

A further aspect of the present disclosure is the use of esterifiedpropoxylated glycerol base oils as biodegradable dielectric fluid.Dielectric fluids are used to cool, insulate and protect the internalsof electronic devices. Typically, these fluids are used in transformers,capacitors, switches, etc. When used in a transformer, for example,dielectric fluids transport heat from the windings and core of thetransformer or connected circuits to cooling surfaces.

Lubricants generally consist of liquid base oil and additives, whereasgrease is a solid to semi-solid product consisting of lubricating oil(base oil) and thickener, unlike other lubricants. According to the ASTM(American Society for Testing and Materials), lubricating grease is asolid or semi-fluid substance containing a thickener agent and alubricating liquid. In grease, the consistency of the product can bevaried by thickening agents such as soap (calcium, lithium, and sodium),complex soap (calcium, lithium, lithium-calcium, aluminum), and bentone-or polyurea-based soap. The manufacturing of grease is a complex processinvolving various chemical reactions produced by different components.Grease are used as an alternative to liquid lubricants where space isrestricted as well as to avoid the leaking and dripping associated withthe liquid lubricants. Renewable and bio-based greases are desired butnatural oils do not sufficiently structure the thickener leading tophase separation and early oiling out of grease compositions. Esterifiedpropoxylated glycerol base oils utilizing diacids and hydroxy functionalacids should have the viscosity and functional affinity for thethickener in a grease formulation limiting or eliminating the phaseseparation seen with other natural base oils.

Process oils or rubber extender oils are special mineral oils derivedfrom refining base oils, mainly as a mixture of naphthenic, aromatic andparaffinic compounds. Process oils have low volatility, low oxidation,high saturation and color stability. They increase the stability andpurity of finished products, making them suitable for application inindustries such as tire, rubber, personal care products, polymers andtextiles. They also have application as a raw material or as aprocessing aid for materials. In the tire and rubber industries, processoil and rubber extender oils functions as an internal lubricant toimprove the blending of rubber formulations and can be used to makeproducts softer, more flexible and even provide insulating properties.The demand for weather-resistant, flexible rubber products makes processoils and rubber extender oils an important ingredient in the productionof automotive tires and other rubber products. Process oils makeproducts softer, more flexible and even provide insulating properties.The demand for weather-resistant, flexible rubber products makes processoils an important ingredient in the production of automotive tires.Process oils also find use in the personal care industry. Theylubricate, soften, smooth, extend, moisturize and add emollience to thefinished product. Natural oils suitable for low temperature applicationstend to consist of significant amounts polyunsaturated fatty acids(PUFA). PUFAs compete during the vulcanization process with multiplecomponents of a functional rubber compound. Esterified propoxylatedglycerol oils do not require PUFA to maintain suitable pour points andwill not compete with rubber components during the vulcanizationprocess. It has been found that natural oils can provide performanceadvantages in tire formulations. Specifically, natural oils, such assoybean oil, have been found to lower the glass transition of tirescreating better cold weather performance. The use of esterifiedpropoxylated glycerol oils enable tailoring of the performance bylowering the glass transition while optimizing the degree ofunsaturation such that an optimal degree of reaction into theformulation can occur. This may include high levels of unsaturation oreven completely saturated fatty acids.

Dielectric fluids are used to cool, insulate and protect the internalsof electronic devices. Typically, these fluids are used in transformers,capacitors, switches, etc. When used in a transformer, for example,dielectric fluids transport heat from the windings and core of thetransformer or connected circuits to cooling surfaces. Where naturaloils are susceptible to oxidation and tend to crystallize at ambientoutdoor temperatures, esterified propoxylated glycerol base oils are notsusceptible to the same degree of oxidation and possess pour points wellbelow those of natural oils.

The lubricant base oil should be miscible with other base fluids forexample the mineral oils commercially available as Group I, II, III, andIII+ base oils, polyaplhaolefins commercially available as Group IV baseoils, and naphthenic, polyalkylene glycol, and esters base oilscommercially available as Group V base oils. The lubricating base oil ofthe present invention may be blended as an additive or compositionalmodifier to enhance the performance of the formulated base oil. Thesynthetic lubricant compositions of the present disclosure show highperformance and high temperature stability and have lubricating andviscometric properties that exceed those of a mineral lubricating oil.The compositions may comprise other conventional oil additives, e.g.antisludge agents, extreme pressure agents, viscosity modifiers, andantioxidants known in the art.

The composition of the present disclosure is illustrated by thefollowing examples.

EXAMPLES Examples 1-72

Mapping Compositional Space of Esterified Propoxylated Glycerol(s)

Given four pure fatty acids (lauric, myristic, palmitic, stearic) wedemonstrate the property effects of compositional changes as a functionof degree of propoxylation. With 24 example compositions per level ofpropoxylation (3, 5, 10) we can map property effects across allcompositions within the three-dimensional design space for each level ofpropoxylation as shown in FIG. 2, which shows 3D design space withsingle fatty acid triesters at the vertices. The results of the mixturedesign and analysis can be seen in Tables A-C, see FIGS. 3-5. Examples34, 45, 53, 58, 69 have pour points above 30° C. and were not analyzedfor kinematic viscosity.

Average molecular weight was calculated from the fatty acid content andthe molecular weight of the propoxylated glycerol. The pour point, seeFIG. 6, pour point data vs. average molecular weight for Examples 1-72,and kinematic viscosity data, see FIG. 7 Kinematic viscosity (40° C.)data vs. average molecular weight for Examples 1-72 and FIG. 8 Kinematicviscosity (100° C.) data vs. average molecular weight for Examples 1-72,were plotted against average molecular weight to observe relativeeffects of changing fatty acid composition and degree of propoxylation.By increasing degree of propoxylation molecular weight increases leadingto increased viscosity while simultaneously depressing pour point forcomparable fatty acid compositions. FIG. 3 shows Table A, whichdescribes examples 1-24; FIG. 4 shows Table B, which describes Examples25-48; and FIG. 5 shows Table C, which describes Examples 49-72.

Mapping of the compositional space enables predictive modelling ofcompositions based on desired performance outputs of the givenesterified propoxylated glycerol materials.

Examples 73-79

Base Oil Comparison Versus Commercial Formulated Lubricant

Examples 73-79, see FIG. 9 Table D, consist of esterified propoxylatedglycerol base oils prepared as known to those of skill in the art andconsisting of fatty acids that are purified sources or whole cutsources. The example base oils (neat and non-additized) were comparedagainst John Deere's HyGard Transmission and Hydraulic Oil which is thestandard fluid for meeting the J20c specification for agriculturalequipment (Table D).

Esterified propoxylated glycerol lubricating base oils displayviscosities characteristic of oils in a given ISO VG range and viscosityindices exceeding commercial mineral oil lubricants. Pour point(s) ofthe example base oils are also characteristic of fully formulatedcommercial lubricants.

Examples 80-84

Functional Fatty Acid Modified Esterified Propoxylated Glycerol

Examples 80-84 consist of esterified propoxylated glycerol base oils inwhich the fatty acid composition has been modified by the addition ofdiacid components and hydroxy fatty acid components, see FIG. 10 Table Eand FIG. 11, Representative functional fatty acids: azelaic, sebacic,and 12-hydroxystearic acids). Example 80 is a base consisting ofhydrogenated coconut fatty acids. Examples 81 and 82 consist ofhydrogenated coconut fatty acids modified with sebacic (C10) diacid.Examples 83 and 84 consist of hydrogenated coconut fatty acids modifiedwith 12-hydroxystearic acid. Pour point and viscosity of the resultantbase oils of the disclosure are clearly impacted by the inclusion offunctional fatty acids in the base oil composition.

Example 85

Dielectric Measurements

Example 85, see FIG. 12, consists of esterified propoxylated glycerolbase oil, comprising propoxylated glycerol (10 PO) and oleic acid, thatwas tested for properties characteristic of dielectric fluids,particularly those utilized as transformer fluids. The base oils of thedisclosure were compared to commercially available biodegradabletransformer fluids, see FIG. 12, Table F.

Examples 86-88

Ethoxylated Glycerol Samples

Examples 86-88 consist of esterified ethoxylated glycerol composed ofethoxylated glycerol Lumulse® 12 (12 ethoxylate units per glycerol) withcoconut fatty acids (Example 86), stearic acid (Example 87), and lauricacid (Example 88). Initial pour point analysis and kinematic viscosityanalysis is shown in see FIG. 13, Table G.

There has been a growing need and desire for environmentally friendlylubricants whether out of a sense of environmental stewardship or due tomandate based on applications and application areas, but currentenvironmentally friendly options are either too costly or have markedperformance issues. Esterified propoxylated glycerol lubricating baseoils provides a high-performance environmentally friendly lubricant thatis cost comparable to Group III+ mineral oils with performance thatexceeds the most costly synthetic lubricants.

While the present subject matter has been described in detail withrespect to specific exemplary embodiments and methods thereof, it willbe appreciated that those skilled in the art, upon attaining anunderstanding of the foregoing may readily produce alterations to,variations of, and equivalents to such embodiments. Accordingly, thescope of the present disclosure is by way of example rather than by wayof limitation, and the subject disclosure does not preclude inclusion ofsuch modifications, variations and/or additions to the present subjectmatter as would be readily apparent to one of ordinary skill in the artusing the teachings disclosed herein.

What is claimed:
 1. A synthetic ester comprising: at least onepropoxylated or butoxylated polyol, wherein an average degree ofpropoxylation or butoxylation is ≥3; at least one fatty acid, whereinthe at least one fatty acid is equal to or greater than C4; and whereina hydroxyl value of the synthetic ester is less than 8 mg KOH/g.
 2. Thesynthetic ester of claim 1, wherein the at least one propoxylated orbutoxylated polyol comprises glycerol, trimethylol propane, neopentylglycol, and/or sorbitol.
 3. The synthetic ester of claim 1, wherein theat least one propoxylated or butoxylated polyol comprises propoxylatedglycerol.
 4. The synthetic ester of claim 1, wherein the at least onefatty acid is substantially fully saturated.
 5. The synthetic ester ofclaim 1, wherein the at least one fatty acid is substantiallyunsaturated.
 6. The synthetic ester of claim 1, further comprising atleast one additional fatty acid having a chain length of greater than orequal to C4.
 7. The synthetic ester of claim 1, wherein a source for theat least one fatty acid is substantially whole cut comprising >80% wholecut fatty acid.
 8. The synthetic ester of claim 1, wherein the at leastone fatty acid is a dicarboxylic acid or dimer acid.
 9. The syntheticester of claim 4, wherein the at least one substantially fully saturatedfatty acid comprises 12-hydroxystearic acid.
 10. The synthetic ester ofclaim 1, wherein the at least one fatty acid is functionalized.
 11. Thesynthetic ester of claim 10, wherein the functionalization comprisesepoxidation, maleination, metathesis, amidation, halogenation,hydration, estolide formation, and/or vulcanization.
 12. The syntheticester of claim 1, wherein the synthetic ester has a pour point of at orbelow −10° C.
 13. The synthetic ester of claim 1, wherein the syntheticester is at least 60 percent biodegradable.
 14. The synthetic ester ofclaim 1, wherein the synthetic ester is at least 50 percent bio-based15. The synthetic ester of claim 1, wherein the synthetic ester forms abase oil.
 16. The synthetic ester of claim 1, wherein the syntheticester comprises a process oil or rubber extender oil.
 17. The syntheticester of claim 1, wherein the synthetic ester comprises a dielectricfluid.
 18. A method for forming a synthetic ester comprising:propoxylating or butoxylating at least one polyol backbone, wherein anaverage degree of propoxylation or butoxylation is from ≥3; esterifyingthe at least one propoxylated or butoxylated polyol backbone with atleast one fatty acid, wherein the at least one fatty acid is equal to orgreater than C4; and wherein the hydroxyl value of the synthetic esteris less than 8 mg KOH/g.
 19. The synthetic ester of claim 1 comprising amixture of at least one aqueous solution, at least one aliphatichydrocarbon fluid, at least one aromatic hydrocarbon fluid, at least onetriglycerides fluid, at least one synthetic ester fluid, at least onepolyolefin fluid, and/or at least one glycol fluid, wherein thesynthetic ester comprises from 0-10% or 90-100% of the mixture.